Megillah, (megillot, plural), Hebrew "scroll," is the
word for each of the "five scrolls" in the Hebrew Bible. The books
of Ruth Song of Songs, Lamentations, Ecclesiastes, and Esther are all referred
to as megillot; but later, Megillah came to refer to Esther alone. The term
also refers to the tenth tractate in the Order Mo'ed in the Mishnah.
A.G.H.

Source:

Bowker, John, The Oxford Dictionary of World Religions,
New York, Oxford University Press, 1997, p. 631